#include <bits/stdc++.h>

 using namespace std;

 const int maxn = ;

 const double eps = 1e-;

 double a[maxn], b[maxn], c[maxn];

 int n;

 double f(double x) {

   double ret = -;

   for(int i = ; i <= n; i++) {

     double y = a[i]*x*x+b[i]*x+c[i];

     ret = max(ret, y);

   }

   return ret;

 }

 double ts() {

   double lo = , hi = 1000.0;

   double ret1, ret2;

   while(hi - lo >= eps) {

     double mid = (lo + hi) / 2.0;

     double mimid = (mid + hi) / 2.0;

     ret1 = f(mid);

     ret2 = f(mimid);

     if(ret1 > ret2) lo = mid;

     else hi = mimid;

   }

   return ret1;

 }

 int main() {

   //freopen("in", "r", stdin);

   int T;

   scanf("%d", &T);

   while(T--) {

     scanf("%d", &n);

     for(int i = ; i <= n; i++) {

       scanf("%lf %lf %lf", &a[i], &b[i], &c[i]);

     }

     printf("%.4lf\n", ts());

   }

   return ;

 }